/Engine/Source/Developer/DesktopPlatform/Public/IDesktopPlatform.h
Opens the "choose font" dialog for the platform
true if font choice was successfully selected
bool OpenFontDialog ( const void * ParentWindowHandle, [FString](API\Runtime\Core\Containers\FString) & OutFontName, float & OutHeight, [EFontImportFlags](API\Developer\DesktopPlatform\EFontImportFlags) & OutFlags )